Confirmation alert when the tab is closed while training

[GuilhermeCaeiro]

Right now, if the tab is closed while a training procedure is going on, the application doesn't provide any alert. I think that the best behavior would be to alert the user about the ongoing training and ask for a confirmation (like Facebook does when you have an unsent message/comment). The objective of that change is to avoid an accidental closing.

[m4nuC]

Good point. I will take care of this during next update. (early next week)